36 



These observations should lie taken daily for one week, an 

 below. 



the results are t<> l»e noted 



To obtain accurate and reliable results it is necessary to use great care in filling the 

 tubes, observing in i^articular that there are no places where the column of soil is 

 unevenly packed or broken by coarse material which will prevent the action of 

 capillarity. 



Expenmeni No. 14- 



EFFECT OF CULTIVATION OR DUST MULCHES ON EVAPORATION OF WATER FROM SOILS. 



Fill all the tubes with the fine prairie soils, using the compacting machine. All the 

 tubes should be filled to the same level. 



The conical bases of thetuliesare then filled i>artly full of water, so that the water 

 shall stand at the same level in each. Determine the level with the S-shaped glass 

 tube, and measure the depth of water very accurately with the millimeter rule. The 

 tubes are to be filled to the same level each day, and the amount of water added is 

 carefully noted. This amount represents the water lost by evapt^ration. The tubes 

 are treated as follows: Tube 1, control; tube 2, cultivated 1 inch; tube 3, cultivated 

 2 inches; tube 4, cultivated 3 inches; tube 5, cultivated 4 inches; tube 6, cultivated 

 5 inches. 



The cultivation is performed each day l)y removing a layer of soil to the depth of 

 cultivation used in the tube, and thoroughly mixing it, when it is replaced. 



Each tube has an area of 80 square centimeters = 12.4 square inches ^jo^V's acre, 

 and the results are to be computed in tons of water evaporated per acre. The obser- 

 vations are to be taken for seven days and the results filled in below. 



Depth of culture 



Total number grams . 

 Tons per acre 



in. 



lln. 



2 in. 



3 in. 



4 in. 



5 in. 



Experiment No. 15. 



EFFECT OF ARTIFICIAL MULCHES UPON EVAPORATION OF WATER FROM SOILS. 



This experiment is conducted in a similar manner to the last, excepting that the 

 tubes are all filled to the same level and used as follows: No. 1, control; No. 2, 2 

 inches sand; No. 3, 2 inches clay; No. 4, 2 inches muck; No. 5, 2 inches sawdust; 

 No. 6, 2 inches cut straw. 



RESULTS. 



Total number grams. 

 Tons per acre 



Control. 



Sand. 



Clay. 



Muck. 



Sawdust. 



Cut straw. 



